A high-temperature energy storage composite dielectric with an ultrathin interfacial layer structure and a preparation method and application thereof

Abstract

The application discloses a high-temperature energy storage composite dielectric with an ultrathin interfacial layer structure and a preparation method and application thereof. The high-temperature energy storage composite dielectric comprises a polymer matrix and interfacial regulation fillers dispersed in the polymer matrix; the interfacial regulation fillers comprise an inorganic inner core and an inorganic interfacial layer distributed on the surface of the inorganic inner core, the inorganic interfacial layer is an ultrathin local interfacial layer in discontinuous distribution, and a local transition interfacial structure is formed between the inorganic inner core and the polymer matrix. The inorganic interfacial layer is formed on the surface of the inorganic inner core through surface reaction, and the thickness can be regulated through reaction conditions. After the interfacial regulation fillers are dispersed in the polymer system, the high-temperature energy storage composite dielectric is prepared through a film-forming and heat treatment process. The application can improve the internal interfacial state of the composite dielectric, relieve local electric field concentration, and regulate the interfacial charge transport behavior, so that the breakdown stability and high-temperature energy storage performance of the material are improved.

Description

Technical Field

[0001] This invention relates to the field of polymer dielectric energy storage materials technology, specifically to a high-temperature energy storage composite dielectric based on the structure regulation of an ultrathin interface layer, its preparation method and application, and particularly to a composite material that improves the interface state and charge transport behavior of polymer composite dielectrics by constructing a local inorganic interface layer. Background Technology

[0002] With the development of power electronic devices and high-temperature electronic systems, higher requirements are being placed on dielectric energy storage materials that can operate stably in high-temperature environments. Polymer dielectrics have attracted widespread attention in the field of high-temperature energy storage due to their high breakdown strength, good processability, and low dielectric loss. Among them, polyetherimide (PEI) is considered a promising high-temperature polymer dielectric material due to its excellent heat resistance and high glass transition temperature.

[0003] However, under high temperature and high electric field conditions, the internal charge transport behavior of polymers is enhanced, which easily leads to uneven electric field distribution, increased dielectric loss, and decreased breakdown strength, thus limiting further improvement in their energy storage performance. To improve these problems, existing technologies typically introduce inorganic fillers into the polymer matrix to construct composite dielectrics, thereby controlling the internal interface structure and electrical properties of the material.

[0004] Furthermore, existing technologies employ a coating layer constructed on the surface of inorganic fillers to form core-shell structures, thereby improving the interfacial state between the filler and the polymer and mitigating localized electric field concentration. However, while improving interfacial stability, existing continuous coating structures tend to weaken the interfacial polarization response and limit the interfacial modulation capability, making it difficult to simultaneously achieve interfacial stability and charge transport modulation effects.

[0005] Therefore, it is necessary to provide a new method for interfacial structure regulation to improve the overall energy storage performance and stability of polymer composite dielectrics under high-temperature conditions. Summary of the Invention

[0006] The purpose of this invention is to provide a high-temperature energy storage composite dielectric and its preparation method, so as to improve the problems of insufficient interface stability, enhanced charge transport, and degraded energy storage performance of existing polymer dielectrics under high temperature and high electric field conditions.

[0007] To achieve the above objectives, the present invention provides a composite dielectric comprising a polymer matrix and an interface-controlled filler dispersed in the polymer matrix; the interface-controlled filler comprises an inorganic core and an inorganic interface layer distributed on the surface of the inorganic core, wherein the inorganic interface layer is an ultrathin local interface layer, which is distributed on the surface of the inorganic core and forms a local transition interface structure between the inorganic core and the polymer matrix to alleviate local dielectric mismatch while retaining some direct interfacial contact between the inorganic core and the polymer matrix.

[0008] A high-temperature energy storage composite dielectric, the high-temperature energy storage composite dielectric comprising a polymer matrix and an interface-controlled filler dispersed in the polymer matrix; The interface-controlled filler includes an inorganic core and an inorganic interface layer distributed on the surface of the inorganic core; the inorganic core is calcium fluoride and the inorganic interface layer is silicon dioxide. The inorganic interface layer is a discontinuously distributed ultrathin local interface layer and does not form a continuous dense coating, thereby forming a local transition interface between the inorganic core and the polymer matrix.

[0009] The preparation method of the high-temperature energy storage composite dielectric includes the following steps: The interface-controlled filler is dispersed in the polymer system; The high-temperature energy storage composite dielectric was prepared by film formation and heat treatment processes.

[0010] Preferably, the preparation of the interface-controlled filler includes: providing an inorganic core, forming an inorganic interface layer on the surface of the inorganic core by a surface reaction method to obtain an interface-controlled filler; the inorganic interface layer is distributed on the surface of the inorganic core and forms a local transition interface structure between the inorganic core and the subsequent polymer matrix, while retaining some direct interface contact between the inorganic core and the polymer matrix.

[0011] Preferably, the sol-gel method specifically includes: Calcium fluoride particles were dispersed in anhydrous ethanol, and deionized water and ammonia were added to form an alkaline reaction system. Tetraethyl orthosilicate was then added dropwise at a rate of 1 drop / min, and the reaction temperature was controlled at 30°C. The thickness of the silica interface layer was controlled by adjusting the reaction time: when the reaction time was 1 h, the local thickness of the silica interface layer was 3-5 nm; when the reaction time was 2 h, the local thickness of the silica interface layer was 9-11 nm.

[0012] Preferably, when using the sol-gel method, the thickness of the inorganic interface layer is controlled by adjusting the amount of silicon source precursor added and the reaction time.

[0013] The present invention also provides the application of the high-temperature energy storage composite dielectric in high-temperature thin-film capacitors, power electronic energy storage devices or high-temperature pulse energy storage devices.

[0014] In some embodiments, the dielectric properties of the inorganic core are higher than those of the inorganic interface layer, and the dielectric properties of the inorganic interface layer are located between the inorganic core and the polymer matrix, thereby forming a gradient interface region within the composite material.

[0015] In some embodiments, the ultrathin interface layer can alleviate local dielectric mismatch between the filler and the polymer, and improve the internal electric field distribution and interfacial charge transport behavior of the composite material.

[0016] In some embodiments, the inorganic interface layer is an ultrathin localized interface layer distributed on the surface of the inorganic core. While mitigating localized dielectric mismatch, it retains some direct interfacial contact between the inorganic core and the polymer matrix. The inventors have discovered that even when the inorganic interface layer does not form a continuous, dense coating, some direct interfacial contact between the inorganic core and the polymer matrix can still be maintained, thus preserving interfacial interactions. This localized interface structure, while mitigating localized dielectric mismatch, also considers interfacial stability and interfacial polarization response, which is beneficial for improving the breakdown stability and high-temperature energy storage performance of composite dielectrics.

[0017] In some embodiments, the inorganic core is selected from fluorides, oxides, or other wide-bandgap inorganic materials; the inorganic interface layer is selected from oxide materials. Preferably, the inorganic core is calcium fluoride, and the inorganic interface layer is silicon dioxide.

[0018] In some embodiments, the thickness of the inorganic interface layer is 1 nm to 100 nm, preferably 1 nm to 50 nm, and more preferably 2 nm to 10 nm.

[0019] In some embodiments, the distribution of the inorganic interface layer is controlled by adjusting the reaction conditions, including the raw material ratio, reaction time, reaction environment, and the amount of silicon source precursor added.

[0020] In some embodiments, the volume fraction of the interface-controlled filler in the composite material is 0.01% to 5%, preferably 0.05% to 1%.

[0021] In some embodiments, the polymer matrix is ​​a high-temperature resistant polymer, preferably polyetherimide.

[0022] The present invention also provides a method for preparing the above-mentioned composite dielectric, comprising the following steps: providing an interface-controlled filler; dispersing the interface-controlled filler in a polymer system; and preparing the composite dielectric by a film-forming or molding process.

[0023] In some embodiments, the inorganic interface layer is formed by a surface reaction, which includes, but is not limited to, sol-gel method, deposition method or surface hydrolysis condensation method.

[0024] Compared with the prior art, the present invention constructs an ultrathin local interface layer structure on the surface of the inorganic core, forming a local transition interface region between the filler and the polymer matrix. This alleviates local dielectric mismatch and local electric field concentration while retaining some direct interface contact between the inorganic core and the polymer matrix, and regulates the interface charge transport behavior, thereby improving the breakdown stability and high-temperature energy storage performance of the material. Attached Figure Description

[0025] Figure 1 The image shown is a transmission electron microscope image of the interface-controlled filler in Example 1. An ultrathin silica interface layer is formed on the surface of the calcium fluoride particles, with a local interface layer thickness of about 4 nm.

[0026] Figure 2 The graph shows a comparison of the breakdown strength of composite dielectrics without an interface layer and composite dielectrics with a localized silica interface layer at room temperature, 150 °C, and 200 °C, under the same filler content (0.25 vol%).

[0027] Figure 3 The graph shows a comparison of the energy storage performance of composite dielectrics without an interface layer and composite dielectrics with a localized silica interface layer under the same filler content (0.25 vol%) at (a) 150 ℃ and (b) 200 ℃.

[0028] Figure 4 High-resolution XPS spectra of PEI / CaF2 and PEI / CaF2@SiO2 systems under the same filler content (0.25 vol%), where (a) is the O 1s spectrum and (b) is the N 1s spectrum.

[0029] Figure 5 The image shows a transmission electron microscope image of the interface-controlled filler in Example 2. The silica interface layer on the surface of the calcium fluoride particles has grown further than in Example 1, and its local interface layer thickness is about 10 nm. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0031] Comparative Example 1 This comparative example provides a high-temperature energy storage composite dielectric comprising calcium fluoride filler and a polyetherimide (PEI) polymer matrix, without constructing a silica interface layer structure.

[0032] Its preparation method includes the following steps: 1) Preparation of calcium fluoride particles 1.5 g of polyethylene glycol (PEG-10000) was added to 100 mL of anhydrous ethanol and stirred until completely dissolved to obtain a dispersion stabilizer solution. Subsequently, 0.6 g of calcium nitrate tetrahydrate Ca(NO3)2·4H2O was dissolved in 5 mL of deionized water to form calcium source solution A; 0.188 g of ammonium fluoride NH4F was dissolved in 5 mL of deionized water to form fluoride source solution B. Under magnetic stirring, calcium source solution A was first added to the PEG-ethanol solution and stirred continuously for 20 min to ensure sufficient dispersion of calcium ions in the system. Then, fluoride source solution B was slowly added to the above mixture and stirred continuously for 30 min to further disperse calcium ions. 2+ With F - A precipitation reaction occurs to form calcium fluoride particles. After the reaction is complete, the precipitate is collected by centrifugation and washed repeatedly with deionized water and anhydrous ethanol to remove residual ions and organic matter. The washed precipitate is then dried to obtain calcium fluoride particles.

[0033] 2) Preparation of composite dielectrics Polyetherimide (PEI) was added to an organic solvent and heated and stirred to form a homogeneous polymer solution. Then, the calcium fluoride particles were directly added to the polymer solution, and the filler was uniformly dispersed by a combination of mechanical stirring and ultrasonic treatment to obtain a composite slurry.

[0034] The obtained composite slurry was cast into a film and then kept at 60 °C for 4 h and 80 °C for 4 h to gradually remove the solvent. Subsequently, the temperature was raised to 200 °C and kept at 200 °C for 12 h for heat treatment, and finally a high-temperature energy storage composite dielectric film was obtained.

[0035] In this comparative example, the volume fraction of calcium fluoride filler in the composite dielectric is approximately 0.25%.

[0036] 3) Structural characterization The resulting composite dielectric film maintains a continuous and dense structure. The calcium fluoride filler is dispersed in the polymer matrix, but no silica interface layer is formed on the surface of the calcium fluoride particles. Therefore, there is no localized ultrathin interface layer structure between the filler and the polymer matrix.

[0037] Performance test results show that without the construction of a localized ultrathin interface layer, the composite dielectric exhibits relatively low breakdown strength and energy storage performance under high-temperature conditions.

[0038] 4) Performance Characterization The breakdown strength and energy storage performance of the obtained composite dielectric were tested. The test results are as follows: Figure 2and Figure 3 As shown in the figure. The results indicate that without the construction of a localized ultrathin interface layer, the composite dielectric exhibits relatively low breakdown strength and energy storage performance under high-temperature conditions.

[0039] Example 1 A high-temperature energy storage composite dielectric includes an interface-controlled filler and a polymer matrix, wherein the interface-controlled filler includes a calcium fluoride inorganic core and a silica interface layer distributed on the surface of the calcium fluoride, and the polymer matrix is ​​polyetherimide.

[0040] Its preparation method includes the following steps: 1) Preparation of calcium fluoride particles Calcium fluoride particles were prepared according to the method in step 1) of Comparative Example 1.

[0041] 2) Preparation of interface-controlled fillers 0.5 g of the above-mentioned calcium fluoride particles were added to 100 mL of anhydrous ethanol and dispersed under ultrasonic conditions for 1 h to obtain a uniform suspension. Subsequently, 5 mL of deionized water and 6 mL of ammonia water were added to the suspension, and stirring was continued for 10 min under high-speed stirring to form an alkaline reaction system.

[0042] Subsequently, 0.5 mL of tetraethyl orthosilicate (TEOS) was added to the above system at a rate of about 1 drop / min. After the addition was completed, the mixture was stirred and reacted for 1 h at 30 °C to allow TEOS to undergo hydrolysis and condensation reactions, and to form a silica interface layer on the surface of the calcium fluoride particles.

[0043] After the reaction was completed, the modified powder was collected by centrifugation and washed four times alternately with deionized water and anhydrous ethanol to remove unreacted precursors and byproducts. The resulting powder was then dried to obtain the interface-controlled filler.

[0044] In this embodiment, by controlling the amount of TEOS added and the reaction time, the resulting silica interface layer is formed on the surface of the calcium fluoride particles, and an ultrathin local interface region is formed between the calcium fluoride particles and the polymer matrix. While alleviating the local dielectric mismatch, it retains some direct interface contact between the calcium fluoride particles and the polymer matrix. The thickness of the local interface layer is about 3 to 5 nm.

[0045] 3) Preparation of dielectric composite materials Polyetherimide (PEI) was added to an organic solvent and heated and stirred to form a homogeneous polymer solution. Then, the interface-modifying filler obtained in step 2) was added to the polymer solution, and the filler was uniformly dispersed by a combination of mechanical stirring and ultrasonic treatment to obtain a composite slurry.

[0046] The obtained composite slurry was cast into a film and then kept at 60 °C for 4 h and 80 °C for 4 h to gradually remove the solvent. Subsequently, the temperature was raised to 200 °C and kept at 200 °C for 12 h for heat treatment, and finally a high-temperature energy storage composite dielectric film was obtained.

[0047] In this embodiment, the volume fraction of the interface-controlled filler in the composite dielectric is approximately 0.25%.

[0048] 4) Structural characterization The resulting silica interface layer is formed on the surface of calcium fluoride particles, and an ultrathin local interface region is formed between the calcium fluoride particles and the polymer matrix. While alleviating local dielectric mismatch, it retains some direct interfacial contact between the calcium fluoride particles and the polymer matrix. The thickness of the local interface layer is about 3 to 5 nm. Figure 4 The XPS results show that, compared to the PEI / CaF2 system, the O 1s and N 1s spectra after introducing the silica localized interface layer still maintain similar variation characteristics to the PEI / CaF2 system, indicating that the interfacial interaction between the inorganic core and the polymer matrix is ​​not completely eliminated after constructing the silica interface layer. The inventors believe that this is related to the discontinuous localized distribution of the silica interface layer, which, while alleviating local dielectric mismatch, still retains some of the interfacial interaction between the inorganic core and the polymer matrix.

[0049] 5) Performance Characterization The breakdown strength and energy storage performance of the obtained composite dielectric were tested. The test results are as follows: Figure 2 and Figure 3 As shown in the figure. The results indicate that after constructing a localized ultrathin interface layer, the composite dielectric exhibits high breakdown strength at room temperature, 150 °C, and 200 °C. Simultaneously, the energy storage density is improved. Compared with Comparative Example 1 and Example 2, this example achieves superior breakdown strength and high-temperature energy storage performance.

[0050] Example 2 This embodiment provides a high-temperature energy storage composite dielectric, whose basic structure is the same as that of Embodiment 1, except that the distribution state and local thickness of the silica interface layer in the interface control filler are different.

[0051] Its preparation method includes the following steps: 1) Preparation of calcium fluoride particles Calcium fluoride particles were prepared according to the method of Comparative Example 1.

[0052] 2) Preparation of interface-controlled fillers 0.5 g of the above-mentioned calcium fluoride particles were added to 100 mL of anhydrous ethanol and dispersed under ultrasonic conditions for 1 h to obtain a uniform suspension. Subsequently, 5 mL of deionized water and 6 mL of ammonia water were added to the suspension, and stirring was continued for 10 min under high-speed stirring to form an alkaline reaction system.

[0053] Subsequently, 0.5 mL of tetraethyl orthosilicate (TEOS) was added to the above system at a rate of approximately 1 drop / min. After the addition was completed, the mixture was stirred at 30 °C for 2 h to allow TEOS to undergo further hydrolysis and condensation reactions and promote the further growth of the silica interface layer.

[0054] After the reaction was completed, the modified powder was collected by centrifugation and washed four times alternately with deionized water and anhydrous ethanol to remove unreacted precursors and byproducts. The resulting powder was then dried to obtain the interface-controlled filler.

[0055] In this embodiment, by extending the TEOS hydrolysis-condensation reaction time, the resulting silica interface layer is further grown than in Example 1, thereby forming a thicker ultrathin local interface region on the surface of calcium fluoride particles, with a local interface layer thickness of approximately 9–11 nm.

[0056] 3) Preparation of dielectric composite materials Following the method of Example 1, the interface-controlled filler was dispersed in a polyetherimide solution, and then cast and heat-treated to obtain a high-temperature energy storage composite dielectric film.

[0057] In this embodiment, the volume fraction of the interface-controlled filler in the composite dielectric is the same as in Example 1.

[0058] 4) Structural characterization The resulting silica interface layer grew further than in Example 1, with a local thickness of approximately 9–11 nm. Variations in the interface layer thickness affect the breakdown strength and energy storage performance of the composite dielectric. As the interface layer thickens further, the interface structure changes, thereby influencing interfacial interactions and interfacial charge transport behavior.

[0059] 5) Performance Characterization The breakdown strength and energy storage performance of the obtained composite dielectric were tested. The test results are as follows: Figure 2 and Figure 3 As shown in the figure. The results indicate that, compared with Example 1, the breakdown strength and energy storage performance of the composite dielectric significantly decreased after further growth of the interface layer. This suggests that the localized ultrathin interface layer structure is beneficial for balancing interface stability and interface polarization response, thereby achieving superior high-temperature energy storage performance.

[0060] Table 1. High-temperature (150 °C) energy storage performance of composite dielectrics with different interface structures

[0061] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention.

Claims

1. A high-temperature energy storage composite dielectric, characterized in that, The high-temperature energy storage composite dielectric includes a polymer matrix and an interface-controlled filler dispersed in the polymer matrix; The interface-controlled filler includes an inorganic core and an inorganic interface layer distributed on the surface of the inorganic core; the inorganic core is calcium fluoride and the inorganic interface layer is silicon dioxide. The inorganic interface layer is a discontinuously distributed ultrathin local interface layer and does not form a continuous dense coating, thereby forming a local transition interface between the inorganic core and the polymer matrix.

2. The high-temperature energy storage composite dielectric according to claim 1, characterized in that, The thickness of the inorganic interface layer is 1 nm to 50 nm.

3. The high-temperature energy storage composite dielectric according to claim 1, characterized in that, The volume fraction of the interface-controlled filler in the high-temperature energy storage composite dielectric is 0.01% to 5%.

4. The high-temperature energy storage composite dielectric according to claim 1, characterized in that, The polymer matrix is ​​a high-temperature resistant polymer.

5. The method for preparing the high-temperature energy storage composite dielectric according to any one of claims 1 to 4, characterized in that, Includes the following steps: The interface-controlled filler is dispersed in the polymer system; The high-temperature energy storage composite dielectric was prepared by film formation and heat treatment processes.

6. The preparation method according to claim 5, characterized in that, The preparation of the interface-controlled filler includes: providing an inorganic core, forming an inorganic interface layer on the surface of the inorganic core by a surface reaction method, and obtaining an interface-controlled filler; the inorganic interface layer is distributed on the surface of the inorganic core and forms a local transition interface structure between the inorganic core and the subsequent polymer matrix, while retaining some direct interface contact between the inorganic core and the polymer matrix.

7. The preparation method according to claim 6, characterized in that, The surface reaction methods include sol-gel method, deposition method or surface hydrolysis condensation method.

8. The preparation method according to claim 7, characterized in that, The sol-gel method specifically includes: Calcium fluoride particles were dispersed in anhydrous ethanol, and deionized water and ammonia were added to form an alkaline reaction system. Tetraethyl orthosilicate was then added dropwise at a rate of 1 drop / min, and the reaction temperature was controlled at 30°C. The thickness of the silica interface layer was controlled by adjusting the reaction time: when the reaction time was 1 h, the local thickness of the silica interface layer was 3-5 nm; when the reaction time was 2 h, the local thickness of the silica interface layer was 9-11 nm.

9. The preparation method according to claim 6, characterized in that, When using the sol-gel method, the thickness of the inorganic interface layer is controlled by adjusting the amount of silicon source precursor added and the reaction time.

10. The application of the high-temperature energy storage composite dielectric according to any one of claims 1 to 4 in high-temperature thin-film capacitors, power electronic energy storage devices or high-temperature pulse energy storage devices.

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